Conventional systems having multiple power supplies (such as battery packs) connected to one or more loads (such as any battery-operated devices) are not able to seamlessly transition between states in which different supplies are connected to different loads. For example, in a conventional system having two batteries and two devices, if the connections between the batteries and devices are to be switched, the devices are first disconnected from their respective batteries, and the devices are re-connected to the other batteries. Connection and reconnection of power supplies and loads disrupt the power supplied to devices, resulting in power dips and spikes. Such power interruptions can at the very least be disruptive to normal operations, and can be unacceptable or damaging in critical or sensitive systems. What is needed is a system able to switch power supplies without interrupting the power supplied to loads.
Moreover, conventional devices incorporating battery packs either use the battery pack to power the device, or charge the battery pack using another power supply (such as a power outlet), as batteries are not traditionally able to be concurrently drained and charged. Vehicles having motors able to run on electrical power, for example, include a battery pack used to power the engine. In vehicles running only on electric power, the battery pack is used to power the engine, and is subsequently recharged using a power outlet when the vehicle is not being powered by the battery pack. In hybrid vehicles, the battery pack is used either to power the engine, or the battery pack is charged by a generator when the hybrid vehicle is not being powered by the battery pack (but rather by, for example, a combustion engine). This practice wastes energy because when the battery pack is being used to power the vehicle, energy that could otherwise be generated (by, for example, a regenerative braking system) and stored in a battery is not being utilized. What is needed is a system configured to run on one battery pack, charge another battery pack, and readily transition between which battery pack powers a device and which battery pack is being charged by a generator.